Monitoring lithium batteries

[WotEver]

1 hour ago, peterboat said:

Balance is inactive because its in green and it says its inactive when it goes to yellow at the beginning of the video its because I have connected the puter to it and activated the BMS. Under normal circumstances I dont connect the puter to it for months so the battery must be balancing by design

At 2:17 you say “the battery is balancing itself automatically...”. That’s what Mastervolt do, with their internal cell-level BMS, and it appears that Valence do the same. That’s separate to the active balance  utility top left. I’m only going by your own description. 

[peterboat]

2 hours ago, WotEver said:

At 2:17 you say “the battery is balancing itself automatically...”. That’s what Mastervolt do, with their internal cell-level BMS, and it appears that Valence do the same. That’s separate to the active balance  utility top left. I’m only going by your own description. 

It only balances if it has a 5 volt source feeding the board like when you connect the computer and it also has to have sufficient amps going in and be near to fully charged 78% must be near to as we saw. If I connect now it wont do anything as they are fully charged [3 amps going in] and they will be more than likely be balanced naturally. I have just connected and they were 2mv out between cells so no need to actively balance. I think the quality of cells help here maybe chinese quality cells might be different?

[WotEver]

Is there a detailed data sheet anywhere for these Valence batteries?

[MtB]

6 hours ago, peterboat said:

Here is the video ta da  if it hasnt worked here is the you tube link https://youtu.be/aDI-Ql3nqxA

 

 

Thanks for the video Peter. Two things strike me.

 

1) This software seems to only deal with cell balancing and record keeping. Does it disconnect the battery on over or undercharge? Or getting too hot?

 

2) The state of your computer screen. It needs a good wash!!

[peterboat]

3 hours ago, Mike the Boilerman said:

 

Thanks for the video Peter. Two things strike me.

 

1) This software seems to only deal with cell balancing and record keeping. Does it disconnect the battery on over or undercharge? Or getting too hot?

 

2) The state of your computer screen. It needs a good wash!!

No it doesnt disconnect Mike I have software and a solenoid to do that, also solar is set to disconnect at 13.8 volts On the drive batteries when they are up to voltage they are diverted to the immersion heater so no waste of solar there. Yes the screen does need a wash!! its a very old puter that I rescued as it has the right windows XP on it to run the Valence software, I will however give it a wash before it goes back in the cupboard for a few months or so

[MtB]

17 hours ago, peterboat said:

No it doesnt disconnect Mike I have software and a solenoid to do that,

 

I thought this was what you were showing us! What software are you using for over and under voltage protection then?

 

What hardware is it running on and how is the computer(?) running it, connected to the relay?

 

Thanks. All very interesting!

[peterboat]

7 minutes ago, Mike the Boilerman said:

 

I thought this was what you were showing us! What software are you using for over and under voltage protection then?

 

What hardware is it running on and how is the computer(?) running it, connected to the relay?

 

Thanks. All very interesting!

In the first instance I use my mppt controller to stop over voltage, as an added protection I bought a little board from amazon for about £6 ish which if the voltage goes over 14.2 it disconnects a solenoid and that cuts off the battery  and now because I have programmed it, it also disconnects with under voltage as well. I would have to look at buyers history  to find the part number but there were lots of them very cheap.

The screen I was showing you was purely to show that the batteries self balance without the aid of BCM, I was also showing that they have temp senders in them and also it has a cycle counter as well.

What surprised me was the batteries have been in a number of months and they are hardly showing any increases in cycles, just shows how little lecce I use

[nicknorman]

Presumably it is showing “full cycle equivalents” ie 4 x discharge to 75% SoC and recharge, would be 1 cycle?

[MtB]

18 minutes ago, peterboat said:

In the first instance I use my mppt controller to stop over voltage, as an added protection I bought a little board from amazon for about £6 ish which if the voltage goes over 14.2 it disconnects a solenoid and that cuts off the battery  and now because I have programmed it, it also disconnects with under voltage as well. I would have to look at buyers history  to find the part number but there were lots of them very cheap.

The screen I was showing you was purely to show that the batteries self balance without the aid of BCM, I was also showing that they have temp senders in them and also it has a cycle counter as well.

What surprised me was the batteries have been in a number of months and they are hardly showing any increases in cycles, just shows how little lecce I use

 

Ok thanks. A quick browse of ebay reveals loads of them too such as this:

 

https://www.ebay.co.uk/itm/12V-Voltage-Control-Delay-Switch-OverVoltage-Under-Voltage-Protection-Module/302699302639?hash=item467a48ceef:g:o6sAAOSwLKpZgh8L

 

[nicknorman]

One presumably want zero power contactors (bistable) rather than relays that need power to keep them on?

[WotEver]

1 hour ago, nicknorman said:

One presumably want zero power contactors (bistable) rather than relays that need power to keep them on?

Yup, I suggested the same some 20 or 30 posts back. 

[MoominPapa]

What sort of voltage measurement accuracy is required from a Lithium BMS system? Have been pondering a prototype using the same technology I used to build a solar system monitor. (Arduino, basically). The can measure voltage with the least significant bit representing 15mV. Is that good enough for balancing, charge termination and under/over voltage trips?

 

MP.

 

[WotEver]

16 hours ago, MoominPapa said:

What sort of voltage measurement accuracy is required from a Lithium BMS system? 

For what purpose? Balancing or protection? I’d have thought that your 15mV would be plenty good enough for protection but nowhere near fine enough for balancing. Most balancing data I’ve seen (including Peter’s video) balances down to 1 or 2 mV. 

[MtB]

25 minutes ago, WotEver said:

For what purpose? Balancing or protection? I’d have thought that your 15mV would be plenty good enough for protection but nowhere near fine enough for balancing. Most balancing data I’ve seen (including Peter’s video) balances down to 1 or 2 mV. 

 

I think people enjoy being anal about cell balancing. I hold that balancing to 15mV will be just fine! Why would finer balancing matter if the cells are being cycled between (say) 20% and 80% SoC?

 

No doubt this is horribly wrong, I await some further edumacation!

[WotEver]

50 minutes ago, Mike the Boilerman said:

 

I think people enjoy being anal about cell balancing. I hold that balancing to 15mV will be just fine! Why would finer balancing matter if the cells are being cycled between (say) 20% and 80% SoC?

 

No doubt this is horribly wrong, I await some further edumacation!

I have no idea, and I’m happy in my ignorance

 

[TheBiscuits]

My understanding is that the internal balancing of the cells (hundreds of them in some cases) is critical to cell lifetimes.  I know Mike thinks that 4 big cells are better than hundreds connected in parallel & series but it seems the big LFP battery manufacturers disagree with him.

 

Certainly the Valence batteries have a whole pile of electronics inside them that the manufacturer thinks are worth installing, and most of it it dedicated to internal cell balance.

 

Remember it is the *equal balance* we are discussing, not the SoC of the whole battery.  If one cell is too low compared to the others it will get damaged. 

 

As a bad analogy, think of a FLA battery - would you use it for a long time with one cell with significantly lower electrolyte than the others, or would you top it up so all cells had the same level & SG?

[MtB]

2 minutes ago, TheBiscuits said:

As a bad analogy, think of a FLA battery - would you use it for a long time with one cell with significantly lower electrolyte than the others, or would you top it up so all cells had the same level & SG?

 

Who accurately measures the level of their FLA electrolyte? I'd predict if accurately measured, every FLA battery on the cut has a variation of 10%

 

 

4 minutes ago, TheBiscuits said:

Remember it is the *equal balance* we are discussing, not the SoC of the whole battery.  If one cell is too low compared to the others it will get damaged. 

.

And if you think properly about how the cell damage occurs, you'll understand the significance of my comment about cell balancing not being critical for users who cycle between 20% and 80%. I stand by that comment unless you can show otherwise!

[WotEver]

48 minutes ago, Mike the Boilerman said:

And if you think properly about how the cell damage occurs, you'll understand the significance of my comment about cell balancing not being critical for users who cycle between 20% and 80%. I stand by that comment unless you can show otherwise!

Let’s take a battery at 80%. One cell is at 104% and dying rapidly, the other three are at 72%. I’d say that cell balance is pretty darned important. 

[MtB]

Just now, WotEver said:

Let’s take a battery at 80%. One cell is at 104% and dying rapidly, the other three are at 72%. I’d say that cell balance is pretty darned important. 

 

I'd also say those cells were more than 0.015V apart from each other.

 

This debate started with me suggesting 0.015V spread across the cells doesn't matter to a user cycling between 20% and 80% SoC. I seem to be getting a stream of posts saying I'm wrong but illustrating with examples WAY outside these parameters.

[MoominPapa]

I think the problem with cell balancing is that it has to happen quite slowly. You need to keep the cells in quite close balance at all times because the differential charge/discharge available for balancing is quite small. If cells are a long way out, then it takes a long time to get them back. If you can only tell that cells are out of balance when one is the the "hockeystick" cell voltage region at low or high SOC then you can't balance until they are a long way out and then it takes a long time to get them back.

 

MP.

 

[BruceinSanity]

The more I read of this thread, the more determined I am to stick with VRLAs! Far too nerdy/techy for me.

 

(The spillchucker just changed techy to tetchy, which seems appropriate. Help, my iPad is reading my mind, shut UP Siri ?)

[cuthound]

3 hours ago, Mike the Boilerman said:

Who accurately measures the level of their FLA electrolyte? I'd predict if accurately measured, every FLA battery on the cut has a variation of 10%

 

Equalising balances specific gravities (to some extent) as well as converting lead oxide to lead and sulphuric acid.

 

Doh, just realised you were talking about electrolyte levels. Well when I started fulltime work back in 1972, I used to top up open toppled FLA cells with a bucket that had calibration marks on the inside ?

Edited September 1, 2018 by cuthound

[peterboat]

I keep on saying this my batteries only balance when the puter is connected, and they are at a high state of charge, and lots of amps are going in, I only connect the puter once a month normally in the evening when charging is finished and all I see is cells that are balanced. Now why its like this is maybe because I only charge to 80%, I dont really work the batteries hard [dishwasher on batteries still at 13.2 on a heat cycle], or the quality of the cells is so high that they balance automatically, my batteries are normally at 13.3 volts at the end of the night except for the one accident when they were 9.4 volts!! Nick gets it so does Mike, I am not the only one doing this, James who supplied the batteries, and JohnV has four of these batteries mixed with lead acids are all seeing the same thing, that restricting the charging keeps the cells in balance. Now we all top balanced the batteries before putting them into service and since then apart from the occasional check on the puter the batteries are doing ok, James and John both have some batteries that have done a lot of cycles and these are still performing like new! I will report back if I see an issue [I have 14 of these batteries] but in all honesty I cant see it happening, as for Dr Bobs question I judge my batteries as being fully charged at 13.8 volts and discharged for me at 12 volts lets see what next year brings shall we?

[eid]

On 18/08/2018 at 15:35, PMB said:

I hope to pop over to Onboard Energy next week to quiz them further as most of my email questions like; how to turn off alternator to avoid too long a charge at acceptable voltage level, have met the "The victron BMS takes care of all that". All well and good but when the whole system will cost nearly as much as a FP genset I'd like a bit more detail.

 

How did this go; did you get the information you wanted? Care to share it? I'm trying to learn as much as I can about a Victron set-up, including the question above.

[Robbo]

5 minutes ago, eid said:

How did this go; did you get the information you wanted? Care to share it? I'm trying to learn as much as I can about a Victron set-up, including the question above.

You can use the BMS12/200 in addition to the VE Bus BMS, in this mode the 12/200 acts as a current restrictor when needed.

 

https://www.victronenergy.com/upload/documents/VE.Bus-BMS-to-BMS-12-1200-alternator-control-cable-EN.pdf

 

The 12/200 is a BMS itself but is limited to 200amp as the batteries are directly connected to it.   If you have need more amps (3kw combi?)  the other BMS talks directly to the combi.

Edited November 28, 2018 by Robbo